package com.jelly.io.nio;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.IntBuffer;
import java.nio.channels.FileChannel;

/**
 * 映射文件性能
 * 
 * @author Jelly
 * 
 */
public class MappedIO {
	private static int numOfInts = 4000000;
	private static int numOfBuffInts = 200000;

	private abstract static class Tester {
		private String name;
		public Tester(String name){this.name=name;}
		
		public void runTest(){
			System.out.println(name+": ");
			try {
				long start = System.nanoTime();
				test();
				double duration = System.nanoTime()-start;
				System.out.format("%.2f\n",duration/1.0e9);
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		
		public abstract void test() throws IOException;
	}
	
	private static Tester[] tests={
		new Tester("Stream Write"){
			public void test() throws IOException {
				DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(new File("temp.tmp"))));
				for (int i = 0; i < numOfInts; i++) {
					dos.writeInt(i);
				}
				dos.close();
			};
		},new Tester("Mapped Write"){
			@Override
			public void test() throws IOException {
				FileChannel fc = new RandomAccessFile("temp.tmp", "rw").getChannel();
				IntBuffer ib= fc.map(FileChannel.MapMode.READ_WRITE, 0, fc.size()).asIntBuffer();
				for(int i = 0 ; i <numOfInts;i++){
					ib.put(i);
				}
				fc.close();
			}
		},new Tester("Stream Read"){
			@Override
			public void test() throws IOException {
				DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream("temp.tmp")));
				for(int i = 0;i<numOfInts;i++){
					dis.readInt();
				}
				dis.close();
			}
		},new Tester("Mapped Read"){
			@Override
			public void test() throws IOException {
				FileChannel fc = new FileInputStream(new File("temp.tmp")).getChannel();
				IntBuffer ib = fc.map(FileChannel.MapMode.READ_ONLY,0,fc.size()).asIntBuffer();
				while(ib.hasRemaining()){
					ib.get();
				}
				fc.close();
			}
		},new Tester("Stream Read/Write"){
			@Override
			public void test() throws IOException {
				RandomAccessFile raf = new RandomAccessFile(new File("temp.tmp"), "rw");
				raf.writeInt(1);
				for(int i = 0;i<numOfBuffInts;i++){
					raf.seek(raf.length()-4);
					raf.writeInt(raf.readInt());
				}
				raf.close();
			}
		},new Tester("Mapped Read/Write"){
			@Override
			public void test() throws IOException {
				FileChannel fc = new RandomAccessFile(new File("temp.tmp"), "rw").getChannel();
				IntBuffer ib= fc.map(FileChannel.MapMode.READ_WRITE,0,fc.size()).asIntBuffer();
				ib.put(0);
				for(int i=1;i<numOfBuffInts;i++){
					ib.put(ib.get(i-1));
				}
				fc.close();
			}
		}
	};
	
	public static void main(String[] args) throws IOException {
		for (Tester tester : tests) {
			tester.runTest();
		}
	}
}
